NEW TYPES
---------
- FileFormatError
- FastaFileFormatError
- PirFileFormatError
- AlignmentConstructionError

MODIFICATIONS
-------------
class Alignment:
- introduced new exceptions to be throw whenever file format error have been detected or any other construction errors occur
- changed accession rules of function getGapCharacter from "public" to "public static"
- new functions:
 * writeFasta
 
class CiffileFormatError:
- changed super class from Exception to the new FileFormatError class

class GraphFileFormatError:
- s. class CiffileFormatError

class PairwiseAlignmentConverter:
- added exception handling features due to class Alignment

class PairwiseAlignmentGraphConverter:
- s. class PairwiseAlignmentConverter

class PdbFileFormatError:
- s. class CifffileFormatError